Temperature control system and apparatus



w. B. MILLER 2,383,811

TEMPERATURE CONTROL SYSTEM ANDLAPPARA'II'US Filed March 13... .194: Z SheetS-Sheet 1 lnventbf' WaHace B. Miller; y z/ mw/ His Attorney.

Aug. 28, 1945 w, a 2,383,811

TEMPERATURE "CONTROL SYSTEM AND APPARATUS Fild March 13, 1943 2 Sheets-Sheet 2 inventor: Wallace B. Miller;

m/ML HIS Att or'ney.

Patented Aug. 28, i945 assasn "ramparts-roar: ooiv {Rog sYs'rEM AND APPAR TU Wallace B. Miller, West Caldwell, N. 5., assignor to General Electric Com New York parry, a corporation of Application March 13, i943, Serial No. 479,087

' '7 Claims. (on. 257 s) ivention; and Fig. 2 shows the year round air The invention relates to temperature control systems and is particularly adapted for air conditioning service. In such servic the invention provides an improved automatic multiple thermostat control system for controlling year round air conditioning equipment so as to obtain automatic selective heating and cooling and ventilating air tempering operation.

A special object is to provide an improved automatic selective multiple thermostat temperature control system that is capable of shifting.

between heating operation of the air conditionconditioner provided with a modified form of multiple thermostatic control system embodying the invention. 1

The year round room air conditioner It, shown schematically in Fig. l, is provided with man heating steam coil ii, a humidifier l2 and an air cooling heat exchanger it; The conditioned air serves as a heat transfer medium that is ciring equipment under control of th room thermostat, ventilating air tempering operation pnder control of a duct air temperature responsive thermostat. and cooling operation under control of the room thermostat in accordance withdifferent predetermined variations in the room tem: perature outside and into a predetermined range. Thus the improved control system and apparatus eliminates the necessity oi manually operating selective heating, cooling, and tempering switches or valve such as heretoforerequired. 'Consequently, the improved temperature control system is particularly advantageousin air conditioning service during spring and fall when heating may be required in the morning, only fresh air tempering at noon, and cooling during the afternoon.

A further object is to selectively render a fresh air tempering control. thermostat ineflective upon cooling operation of the air conditioner under the control of the room thermostat, and eiiective to control the fresh air tempering operation of theair conditioner only after a subsequent heating operation thereof under control of the room thermostat.

A more specific object is to provide automatic interlocking means for enabling the room thermostat to transfer the control of a reversible motor operated valve that effects the room heatin operation of the air conditioner to a duct airtem-' perature responsive thermostat so as to e'ilect 4 ventilating air tempering operation thereof, while insuring that the heating valve is always closed upon room cooling operation of the conditioner under control of the room thermostat and thereafter remains closed vuntil a room heating operation of the conditioner occurs.

' Otherobiects and advantages of the invention will be pointed out in the followingvdescription of the accompanying drawings in'which Fig. 1 schematically shows a year round air conditioner 'having a multiple thermostatic control system embodying the improvements of the present inculated by th motor driven blower l4 through the duct it into'theroom 68;.- Recirculated air from room it is supplied tothe conditioner it through the duct ll, the flow being controlled by dampers 58-. Fresh Atlr for ventilation is admitted to the conditioner it through. the duct 88 with the flow controlled by the damper 23.

Steam is supplied to the air heating coil ii under the control or the reversible motor operated valve 25 having the driving motor 26 provided with a. closing winding Zl and an opening winding .28. Motor 26 drives through suitable speed reducing gearing (not shown) the disc 30 which opens and closes the valve 25 bymeans of the connecting rod 34. As shown diagrammatically in the drawings, the disc 30 also may be provided with a point cam 30a for opening the closing limit switch 3| when the valve is in its closed position and opening the opening limit switch 32 when the valve is in the open position. A special interlocking switch 33 is normally biased to the circuit opening position and.

is arranged to be closed only when the steam valve 25 is in it closed position.

The reversible valve operating motor 26 is, in 4 thermostat 36, the former being able only to energize the motor to open the valve 25 in response to a dropin the temperature of the room It and the latter being able to energize th mo-' tor 26to both close and open the valve 25 in response to variations'in the temperature of the air supplied through the duct It from th conditioner It to the room. Thus according to the present invention, the Joint thermostatic reversing motor control arrangement is such that the valve 25 will be'operated to its open-position to admit steam to the air heating coil H whenever the room temperature falls below ,a predetermined minimum desired value. to which the room thermostat 35 is set. However, when the room temperature rises above the minimum'desired' value to which room thermostat 35 is-set, then the reversing control of the valve operating motor as is automatically transferred to the duct thermostat 36 so as to enable the air heating coil 2,ses,s11

' responsive heating control thermostat 35 will II to variably temper the fresh ventilating air circulated to the room l6 and thus always maintain the temperature of the ventilating air supplied to the rooin through the duct l above a predetermined value that will not cause discomfort. The improved reversing motor transfer circuit arrangement whereby this desirable result is obtained is described hereinafter in connection with the operation of Fig. l.

The operation of the humidifying apparatus l2 may be controlled by an electromagnetic valve 31 for regulating the admission oi water to a distributing tank 38 from which it falls over the humldifying screens 39 into'the drain tank 40. The energization of the humidifyin'g valve- 31 preferably is controlled by a humidostat ll with the interlock switch 42 provided to insure that humidification can occur only when the steam valve is in its Iully open position.

The air cooling heat exchanger 13 comprises a refrigerant evaporator that is connected by a refrigerant line 50 with the compressor 5! so as to withdraw the refrigerant medium that is evap-. oratedin the heat exchanger 13. The medium,

'aiter passing through the compressor 5 I, is supplied to a condenser 52, from which the condensed liquid flows into the receiver 53. Liquid refrigerant is then supplied from the receiver 53 through the refrigerant line it under the control of the thermostatic expansion valve 55 to the evaporating coils of the air cooling heat exchanger IS. The compressor 54 is perated by the motor 58 which is energized under the control of theroom cooling control thermostat 51 when the room temperature exceeds a predeterminedmaximum desired value.

- In accordance with the present invention, the minimum temperature responsive'room heatin control thermostat 35, the duct air temperature responsive tempering control thermostat 3S and the maximum temperature responsive room cooling control thermostat 57 are interlocked in a selective thermostatic control system such that whenever the cooling thermostat Ill starts the compressor 5| into operation at the maximum temperature, the steam valve 25 will always be closed and cannot be reopened except under the control of the room heating control thermostat 85 at the minimum temperature, The selective interlocking arrangement is such that the duct air temperature responsive thermostat 36 is rendered eflective to control the closing and opening 01' the steam heating valve 2! only when the room temperature rises into the temperature range betwen the minimum and maximum values, but is rendered ineffective upon a call for cooling operation by the room cooling thermostat 51 and re- 1 mains ineffective until after a subsequent call the room thermostat 35.

Operation of Fig. 1

The motor 8| that drives the air circulatins blower ll preierablyis connected to be energized from the supply lines Ll, L2 upon closure 0! main power supply switch H, the circuit extending for heat by action of the conditioner i8 whenever the room from supply line Ll, through conductors l2, l8,

motor ill, conductors II and ll to supply line L2. Thus, the air circulating blower ll will operate continuously as long as the main power supply I switch it is closed. Whenever the room temperature falls below thepredetermined minimum value at which heating operation o! the air conditioner II is desired. the room air temperature ating motor 26. This circuit may be traced from w the secondary of transformer 81 through conductor 68, the blade 35a in engagement with contact C, conductors 59 and 10, the limit switch 32, the motor opening winding 28, andthence through conductor H to the other side of the secondary transformer 51. As a result, motorZB will operate the disc 30 to open the valve 25 and admit steam to the air heating coil l I. when the steam valve 25 is operated to its fully open position, the cam point 30a. 01 disc 30 engages with the limit switch 32 to open the energizing circuit for the opening winding 28. However, valve 25 will remain in the fully open position so as to continue to supply steam to the air heating coil I i.

When the resulting transfer of heat from the conditioner I0 to the room it through the medium of the circulating air raises the temperature of room l8 suificiently to effect the movement of the blade 35a of the room thermostat into engagement with'the contact H, then the selective control of the energization of the valve opening and closing windings 27 and 28 is transferred to the duct thermostat 36. This control transfer circuit may be traced from the secondary of transformer 61 through conductor 68, the blade 35a of the room thermostat in engagement with contact H, conductor is, interlock contact M of the interlocking relay 76, conductor 16, to the blade 36a oi the duct thermostat 36. In case the temperature of the air. circulated to room l6 through the duct '05 re-.

, closing winding 21 will be energized through'a circuit extending from the blade of duct thermostat 38 through contact H, conductor 18, limit switch 3!, closing winding 21, and conductor H. Thus, after the temperature of room l6 has been raised into the range in which the room heating control thermostat 35 becomes satisfied, the duct thermostat 8B is rendered effective to close or open the steam valve 25 so as to produce a sufilcient heating action in the air heating coil H to temper the ventilating air circulated into the room 16. In this way the temperature, of the ventilating air may be maintained at a desired value, irrespective of the manual adjustments or the dampers I8 and 20, and irrespective of the temperature of the fresh air supplied through the duct ii. In ordinary service, the room heating control thermostat 35 may be set to produce room heating temperature falls below some minimum desired value such, for example, as 70. The duct thermostat a may be set to maintain the ventilatihs air at substantially the same temperature 0! 70 or, if desired, at" either a lower or higher tem-;

perature. In any case, the air tempering control action of the duct thermostat ll effectively insures against circulation of ventilating air at a low temperature such that discomfort might result. 1

The room cooling control thermostat l1 ordi- 51. the interlock relay I can be opened is by the formed BI through the conductors 82 and 83.

The resulting closure of relay contact M- will complete the energizing circuit for the compressor driving motor 56 throughthe conductors 85, 86. As a result, the compressor 5| is started into operation towithdraw heat from the heat exchanger I3 and thereby cool the air supplied from the'conditioner to to the room I6.

When the compressor starting relay 80 closes,

the auxiliary contact 8? thereof completes an energizing circuit for the interlock relay I5 exthe contact C and energize the opening winding 2a through the circuit previously traced to effect the opening of the steam valve 25. When this occurs,,the special valve lnterlock swltch 33 opens the holding circuit of the interlocking relay to enable this relay to return to the position to which it is biased, as shown in the drawings. This returns the double function contact it to its lower circuit closing position, in which it is shown, so as to again transfer the control of thesteam'valve to the duct thermostat 36 when the room thermostat 35 engages its blade 35a with contact H. This latter will tending from the secondary of transformer 90 through conductor 95, the operating ,winding of relay I5, conductor '92, auxiliary contact 81! in its closed position, and conductors 93 and 94. Thereupon interlock relay 15 operates its double function contact it to render the duct thermostat 36 inefi'ective to control the motor operated valve 25 by opening the control circuit to the duct thermostat blade .3611 through conductor At the same time, the double function conit. tact It completes a safety circuit for energizing the closing winding 27 of the motor 26; this circuit extending from the secondary of transformer 61, conductor 6B,;the blade 35a of the heating control thermostat in engagement with contact H, conductor i3, contact It in itsupper circuit closing position, and thence through conductors 95 and i8, limit switch 3!, closing winding 27, and conductor Ii.

The establishment of the safety energizing circuit for closing winding '27 insures that the motor 26 will operate the steam control valve 25 to the closed position thereby closing the special valve interlock switch 33, as shown in the drawings, independently of the control of the duct thermostat 36 in case the valve 25 and switch 33 are not already in the closed position. However, under normal operating conditions, the steam valve 25 will ordinarily be closed before the room temperature reaches the maximum desired value at which the cooling thermostat 5i closes its contacts. In any case, when the interlock relay -15 is energized, the special valve a holding circuit for maintaining the interlock relay l5 energized independently of the auxiliary contact 87 of the compressor starting relay 80. relay I5 extends from the secondary of transformer 90 through conductor 9i, relay winding holding circuit serves to maintain the interlock relay I5 energized and thus maintain duct thermostat 3B inefiective not only while the compressor 5| is in operation, but as long thereafter as the room temperature remains 'withinthe predetermined temperature range havingminimum and maximum limits determined by the setting of the the room heating thermostat35 and the setting of the room cooling thermostat The only way that the holding circuit of room temperature falling below the minimum value at which the room heating control thermostat '35 is set to engage its blade 35a with The holding circuit for the interlockoccur only when the temperature of the room it rises into the-temperature range that is determined by the settings of .the room heating control thermostat 55 and room cooling control.

thermostat 57.

Operation of Fig. 2

In the modified temperature control system shown in Fig. 2, a double contact room heating and cooling control thermostat W0 is combined with an intermittent overlapping double contact circuit opening and closing device of the type more fully described and claimed in the-Crago Patent 2,202,731 for controlling thev operation of the air conditioner I0 in conjunctionwith the duct thermostat 36. This modified system operates as follows. When the room temperature falls below the heating limit of the temperature range to which the thermostat 900 is adjusted, the blade engages with the contact C4. Then, when the intermittent contact IOI is closed by the cam I02 that is continuously operated by the timing motor I 03, an energizing circuit forthe steamvalve control relay IN is established from the secondary of transformer I05 through conductors I05, the closed contact IOI, conductor M7, the blade I000. of the room thermostat in engagement with contact C4, conductor I08, the operating windingof relay Hit, conductor 509. As a result, relay let moves both its contacts H0 and Iii from their lower circuit closing positions, in which they are shown, to their upper circuit closing positions; Contact H0 in its upper circuit closing position establishes an energizing circuit from the transformer secondary winding H2 through conductors IE3, M0, M5, limit switch 32, the valve opening motor winding 28, conductor lit to efiect opening of the steam supply valve 25. When valve 25 reaches the full open position, the cam point 30a of disc 30 opens the limit switch 32 and the valve 25 continues to supply steam to the air heatingcoil it so as to efiect arise in the room temperature due to the transfer of heat by the circulating air heat transfer medium. I

Contact I05 in its upper circuit closing position cooperates with the periodic contact I20 when it is closed by cam I2i before contact I0! is opened by cam I02 to establish a holding 'circuit for relay IM, this holding circuit extending from the secondary 'of transformer I05 through conductor I06, conductor I22, contact I20 in its circuit closing position, conductor I23, contact iii in its upper circuit closing position, relay 06, and conductor I00. As a result,.relay it will be deenergized in case the thermostat blade 500a disengages contact C4 as soon as contact !20 opens therebyretuming both the relay contacts H0 and ill to their lower circuit closing positions. Contact H0 thereupon transfers the control of the valve operating motor to,

tending from the transformer secondary II2 through conductors 3, contact IIO, conductor I25, contact I28 of the interlock relay I21 in its lower circuit closing position, conductor I28 to the blade 38a of the duct thermostat. Thus,when the air supplied from the conditioner I is above the predetermined tempering value, the blade 38a of duct thermostat 36 will engage with its contact H1 so as to establish an energizing circuit through conductors I29 and I30, limit switch 3I, closing winding 21 and conductor 8 to effect the closure of the steam valve 28. However, when the temperature of the air supplied to the room I8 through duct I8 falls below the desired tempering value, the blade 38a of duct thermostat 36 engages with its contact C1 to establish a circuit through conductors I05 and H5, limit switch 32, opening winding 28, and conductor I I8 to effect opening of the steam valve 28.

In this way the room thermostat I00 and the 1 duct thermostat 38 jointly control the opening and closing of the steam valve 28 to eflect room heating and circulating air tempering operation of the conditioner I0, the room thermostat I00 being effective to initiate room heating operation when the room temperature falls below the lower limit of the temperature range to which the room thermostat I00 is set, and the duct thermostat being eflective to initiate duct air tempering operation when the room temperature rises into this range.

Upon an increase in the room temperature the upper limit of the range between the heating and cooling settings of the thermostat, the blade I0l-will engage with its contact 34. Thus, when the periodic contact IOI closes a circuit from transformer secondary I08 is established through conductor I08, contact IOI, conductor I01, blade thermostat I00a in engagement with contact H4, conductor I 38, theopaseasif former I82 through conductor 183, the winding crating winding of control relay I31, conductors I38 and I09. As a result, contacts I and I4! of the control relay I31 are closed. The closure of contact I40 serves to establish a holding circuit for control relay I81 through conductor I42, contact Ill, conductor I23, periodic contact I20 when it closes before contact IOI opens, conductors I22 and I08. As'a result, control relay I31 will be maintained energised for a limited period even though the blade of room thermostat I00 engages contact H4 only momentarily.

Closure of contact I establishes an energizing circuit extending from transformer secondary I43 through conductor I44, the operating winding of the compressor starting relay I48, conductor I48, contact I, and conductor I41.

The resulting closure of main contactl80 energizes the compressor driving motor 58 and thereby. starts air cooling operation of the conditioner I0. At the same time, the closure of auxiliary contact I8I completesa circuit from the trans- ,iormer secondary I52'through conductor I83, the.

operating winding of the interlock relay? I21; conductor I84, contact I8I, and conductors llil'and I88. As aresult the-interlock relay I21 operates its contact I28 from its lower circuit closing position into its upper circuit closing position? This performs two control functions. First, the duct thermostat 38 is rendered ineflectivesince thecircuit to the blade 38:: of the thermostat is opened. The second function is the closure of a safety circuit that will energize the valve closing of interlock relay I21, conductor IN, the valve interlock switch I33, conductor I82, auxiliary contact I80, and conductor I88. The valve inter-t lock switch I33 is closed when the valve is operated to its closed position and through the holding circuit maintains the interlock relay I21 energized until valve 25 is operated from its closed a position. Thus, even thoughgthe room thermostat blade l00a disengages contact H4 so that relays I31 and I45 are both deenergized upon the subsequent opening of periodic contact I20 so as thereby to stop the air cooling operation of the compressor 5|, still the holding circuit of the interlock relay I21 remains energized solely under the control of-the valve interlock switch I33. This serves to maintain the duct thermostat I0 ineffective after an air cooling operation of the conditioner I0 even though the room air temperature should decrease into the range between the lliggting and cooling settings of the thermostat In case the room temperature decreases to the heatingsetting of thermostat I00, then the steam valve 25 will be opened in the manner previously 'descri-bed'to eiiect an air heating'operation of the conditioner I0. Upon the opening of valve 25, the interlock switch I33 is opened thereby opening the holding circuit of the interlock relay I21. As a result, the interlock contact I26 is returned to its lower circuit closing position in which it is shown so as thereby to transfer the control of the closing and opening of valve 28 to the duct thermostat 38 when'the blade I00 oi the mo thermostat -disengages contact C4, and relay I 4 is deenergized so as to return contact I I0 to itslower circuit closing position to complete the control transfer to the duct thermostat 3841 through conductors I28 and I28; Thus, it will be seen that the duct thermostat 88 is rendered ineffective to control the opening'and closing of the steam valve 25 as soon as air cooling opera- 7 tion of conditioner I0 is initiated, and that the interlock relay I21 serves to maintain the duct thermostat 38 inefi'ective thereafter until after the. room temperature decreases sufllcientiy to effect a heating operation of the conditioner II and then rises within the range between the air cooling and air heating settings of the room thermostat m.

What I claim. as new and desire to secure by letters Patent of the United States is:'

In combination, a space air conditioner havingair circulating means provided with means for mixing fresh'air'with the circulated air, means for heating said mixturepincluding' a reversible motor operated steam valve, means for cooling said mixture including a separate motor operatedcompressor, thermostatic-control means. responsiveto the space temperature for operating said compressor when the space temperature rises above a predetermined temperature range. and $0.?

opening said steam valve when the space tem-' perature falls below said predetermined temperature ran e, a separate thermostatic control means responsive to the temperature of said mixture, and means under control of said first thermostatic control means for rendering said separate thermostaticcontrol means eifective to control the closing and opening of said valve in accordance with variations in e temperature of said mixture only when the space temperature rises into said range.

2. In combination, a thermostatic control mechanism responsive to the temperature of a space, air conditioning apparatus having means for supplying air to said space and having air heating means'and air cooling meanspperable' under control of said control mechanism for selectively heating and cooling-:the air supplied to said space when the temperature of said space varies respectively below and above a predetermined temperature range, and'means including a thermostatic control'device responsive to the temperature of the air supplied to said space and rendered effective under control of said space temperature responsive control mechanism for operating said air heating means to temper the air supplied to said space when the temperature of said space rises into said range.

3. In combination, a space air conditioner, having a fresh air inlet and having air heating and cooling meansprovided with thermostatic control mechanism for responding to the temperature of said medium and rendered effective under control of said space temperature responsive control mechanism for regulating the temperature of said medium only when the temperature of 'said space rises into said range.

5. In combination, cooling control means including a thermostat, heating control means including a thermostat and a reversible motor operating valve under control of said thermostat, and a separate thermostat having means for reversibly operating said valve rendered ineffective vunder the control of said cooling thermostat and Y dition varies into said range from outside one ture of the space to selectively heat or cool the air supplied to said space when the temperature of saidspace varies respectively below and above a predetermined temperature range, and means including a thermostatic device responsive to the temperature of the air supplied to said space and rendered effective under control of said space temperatureresponsive control r'nechanism for regulating the temperature of the fresh air supplied to said space when the temperature of said space rises into said range.

4. In combination, means .including thermostatic control mechanism responsive to the temperature of a space for selectively heating and cooling a heat transfer medium for saidspace eflective under the control of said heating control, thermostat.

6. In combination, means including a first teme perature responsive device for oppositely chang-' ing a temperature condition upon opposite variation thereof outside a predetermined range, and

means including a second automatic temperature responsive device responsive to a second temperature condition thermally influencing said first temperature conditionfor regulating said second temperature condition and having interlocking means selectively controlled by said first automatic temperature responsive device to render said second automatic temperature responsive device eflective when said first temperature conpredetermined limit thereof and ineffective when said first condition varies into said range from outside the other limit thereof.

7. In combination, means including a first automatic temperature responsive device for oppositely changing a temperature condition upon opposite variation thereof outside a predetermined range, and cooperating means including a second automatic temperature responsive device responsive to a second temperature condition when the temperature of said space respectively falls below and rises above a predetermined temperature range, and means including a separate thermostatic device responsive to the temperawarmer: n. imam. 

